Lightening Flashes ( speed of light) and we count off seconds until the thunder ( speed of sound) comes. Roughly 5 seconds to a mile to gauge distance of coming storm.
A Michigan Harbor was using flash / sound system of sending radio beam (lamp) and fog horn sound (resistor at top) at the same time. A boat captain would hear radio beam sound and count seconds until he heard the fog horn to guide his ship into the harbor. If 10 seconds was counted he knows he is two miles approximately from the lighthouse.
It seems if we are talking to someone on a cell phone or radio transmitter and a shot or loud sound is at their location we start stopwatch with over phone sound and hold phone away from our ear and press stopwatch when sound reaches our location to phone and sound calculate a small distances from the one on telephone.
